1. Field of the Invention
The present invention is generally related to surgery. In particular, the present invention relates to suturing with synthetic suture material.
2. Description of the Related Art
For many years, surgeons have reconnected tissue using suturing and other methods. Suturing is a surgical technique involving the connection of tissue by stitching the tissue together with a strand of appropriate suturing material. Synthetic or polymer sutures are among the class of appropriate suturing material.
Typically, a suture is prepared by piercing the suture through tissue on both sides of a wound, by pulling the ends of the suture to bring the sides of the wound together, and tying the suture into a knot. The knot preserves the tension on the suture to maintain the sides of the wound in approximation and allow the tissue to heal.
Generally, it is undesirable for the suture to slip and become untied. An improperly tied knot can slip and untie at a tension far lower than the tension required to break the suture. When the suture is internal to the body, replacement of the failed suture can require another surgery.
Synthetic sutures are available as monofilament (single strand) or polyfilament (multiple strands). Polyfilament sutures can exhibit less shape memory and more friction than monofilament sutures, thus rendering a conventional knot made from polyfilament suture relatively more resistant to slippage than a conventional knot made from monofilament suture.
However, monofilament sutures (sutures made from one strand) are preferred in many applications. One such application is arthroscopy, where a surgeon accesses the surgical area through a hollow tube known as a cannula. In arthroscopy, the surgeon passes a suture through the cannula to the tissue. Conventional arthroscopy tools do not permit the direct passage of a polyfilament suture, as the polyfilament suture is too flexible. Thus, to use a polyfilament suture, the surgeon must first pass a monofilament suture (xe2x80x9cfeeder linexe2x80x9d) first, and then pull the polyfilament suture through the tissue using the monofilament suture. Cumulatively, the extra steps of first passing monofilament sutures can undesirably add a significant amount of time to a surgical procedure and can increase the trauma and anesthesia risk endured by a patient. Surgeons also prefer monofilament sutures in situations where a wound site may be contaminated. In those situations, monofilament sutures can lessen the risk of infection.
One drawback to monofilament sutures is that knots tied with monofilament sutures can slip and become untied more readily than polyfilament suture. Monofilament suture has a smoother exterior surface than polyfilament suture and thus exhibits less friction to prevent a knot from slipping. Monofilament suture also tends to exhibit more xe2x80x9cmemory,xe2x80x9d i.e., monofilament suture has a greater tendency to return to a previous form, such as an untied form.
Prior techniques to improve the security of a knot made from a monofilament suture have proven inadequate. One prior technique includes tying a knot with extra throws to reduce the tendency of the knot to slip. Extra throws, however, disadvantageously increase the bulk of a suture, consume extra time to process, and require extra space, which is not always available.
Additionally, proper knot tying techniques are not always followed. For example, through inadvertence or inexperience, the disfavored and easily loosened xe2x80x9cGranny knotxe2x80x9d can be accidentally tied instead of a xe2x80x9cSquare knot,xe2x80x9d which is a relatively more secure knot.
Embodiments of the present invention advantageously improve the security of knots. Surgical knots tied in accordance with an embodiment of the present invention can be tied with fewer throws, in less time, with more security, and with more resistance to incorrectly tied throws. According to one embodiment, a monofilament knot in arthroscopy can advantageously combine the resistance to slippage of a polyfilament suture and yet retain the advantage of not requiring the extra step of passing a feeder line.
One embodiment of the present invention places the ends of a knot in contact with each other and fuses the ends together with heat. The extraneous end portions of the suture are then cut, leaving the fused portion behind to prevent the knot from slipping. Preferably, the fused portion is about 3 millimeters (mm) long. The heat can be advantageously applied in a liquid environment, such as inside a human body.
Another embodiment of the present invention applies heat to the limbs of the knot such that the limbs deform. The deformation renders the knot more resistant to slippage. Again, the heat can be applied within the liquid environment of a human body.
Another embodiment of the present invention applies heat to the last throw of the knot. The last throw of the knot already has strands in contact with each other. The applied heat fuses the strands together and inhibits the tendency for the knot to loosen through slippage. The heat can again be applied within a liquid environment.